Analysis of brain tissue for narcotic agents by the usual biopsy methods is inadequate because it yields only average results rather than localization data associated with specific individual cells. The precise localization of the drug in situ is crucial in any attempt to correlate drug localization with histologic structure. High resolution autoradiography makes possible the direct examination of individual cells in a heterogenous population providing the drug under investigation is not extracted or translocated but remains in situ during the entire process. New autoradiographic procedures developed in these laboratories for diffusible substances now make such studies possible because these procedures utilize freeze-dried frozen sections. This new dry autoradiographic technique excludes all treatment of the tissue involving the use of solvents and of exogenously administered labeled drugs. The technique has been extended to generate information on the nature and concentration of biogenic amines in the self same section of tissue used in the autoradiographic procedure. Correlative studies on the cellular localization of agonists and antagonists, can thus be carried out utilizing immunofluorescence and immunoautoradiography when specific antibodies are available for each antibody. These techniques, when combined, provide the opportunity to determine the localization of labeled narcotic agents on/or in specific cells, to determine the effect of antagonists on localization of agonist, and to identify the cell types involved with regard to catecholamine content as measured by microfluorescent procedures, and by histochemical staining in the last and final step.